Surface mount RC devices

ABSTRACT

Both discrete and array RC components are described using cofireable resistive material as part of internal electrodes of the device. The devices include a sintered body of multilayer ceramic material in which multiple first and second electrode layers are stacked. Each of the first layers comprises at least one resistive electrode pattern extending across the sintered body between respective pairs of terminations. The second layers comprise an electrode pattern extending transverse to the resistive electrode pattern, such as between end terminations. In some embodiments, opposing side electrodes serve as input and output terminals of a respective feedthrough filter. In a feedthrough arrangement, the third terminal may be provided by one or both of the end terminals. The invention also describes an improved termination structure including a layer made from a metal oxide material.

[0001] This application is a divisional of U.S. Ser. No. 09/335,991,filed Jun. 18, 1999.

BACKGROUND OF THE INVENTION

[0002] The present invention relates generally to the art of surfacemount electronic components. More particularly, the invention relates toelectronic components of the type having a multilayer ceramic structure.

[0003] Multilayer ceramic capacitors (MLCs) have enjoyed widespread usein the electronics industry. These devices are generally constructedhaving a plurality of ceramic-electrode layers arranged in a stack.During manufacture, the stacked layers are pressed and sintered toachieve a substantially unitary capacitor body. The capacitor body isoften rectangular in shape, with electrical terminations of oppositepolarity provided along respective sides or at opposite ends. A singleMLC package may contain one capacitor, or an array of multiplecapacitors.

[0004] For a variety of considerations, including a desire to conservecircuit board “real estate,” several types of integrated passive devices(IPDs) have been provided. For example, integrated RC devices, producedin a manner similar to MLCs, utilize a single “package” to yield adesired filtering function. Often, the capacitor of these devices willbe made in a manner substantially identical to discrete MLCs. Theresistor, electrically connected to the capacitor in a predeterminedmanner, is often applied to the outer surface of the ceramic body.

SUMMARY OF THE INVENTION

[0005] The present invention recognizes various disadvantages of priorart constructions and methods. Accordingly, it is an object of thepresent invention to provide novel electronic devices having amultilayer ceramic structure.

[0006] It is a further object of the present invention to provide novelintegrated passive devices (IPDs) for surface mount applications.

[0007] It is an additional object of the present invention to providenovel RC components having a multilayer ceramic structure.

[0008] It is also an object of the present invention to provide amultilayer ceramic device having a novel termination structure.

[0009] Some of these objects are achieved by a composite RC devicecomprising a device body defined by a plurality of first ceramic layersand a plurality of second ceramic layers arranged to form a stack. Eachof the first ceramic layers has at least one first electrode platethereon, and each of the second ceramic layers has thereon a secondelectrode plate. A predetermined number of the first ceramic layers arerespectively adjacent to a corresponding one of the second ceramiclayers such. that the first electrode plate will oppose the secondelectrode plate to form two plates of a capacitor.

[0010] In the composite RC device, either or both of the first electrodeplates and the second electrode plates are at least partially formed ofa cofirable resistor material. In addition, the device body has a pairof terminations electrically connected to the first electrode plate oneach of the first ceramic layers. Furthermore, at least one terminationis electrically connected to the second electrode plate on each of thesecond ceramic layers to provide a predetermined electrical function.

[0011] In some exemplary embodiments, each of the first ceramic layerscomprises a plurality of side-by-side first electrode plates. Thesefirst electrode plates extend between respective first and secondterminations located on the device body. For example, a total of fourside-by-side first electrode plates may be provided on each of the firstceramic layers.

[0012] Often, the second electrode plates may extend between third andfourth terminations on the device body. In such cases, the firstelectrode plates may extend in a direction transverse to the secondelectrode plates. In addition, the first electrode plates and the secondelectrode plates may each be formed having a wider main plate portionwith narrower tab portions at each end thereof.

[0013] In other embodiments, each of the first ceramic layers maycomprise a single first electrode plate extending between first andsecond terminations located on the device body. In this case, the secondelectrode plates may extend between third and fourth terminations on thedevice body. For example, the second electrode plates may extend in adirection transverse to the first electrode plates. Often, the firstelectrode plates and the second electrode plates may each be formedhaving a wider main plate portion with narrower tab portions at each endthereof.

[0014] Preferably, the first electrode plates include the cofirableresistor material. Resistor materials suitable for this purpose mayinclude an appropriate metal oxide (such as ruthenium oxide) which,depending on the exigencies of a particular application, may be dilutedwith a suitable metal. The second electrode plates, on the other hand,may be formed of a substantially nonresistive conductive material.Materials suitable for this purpose may be selected from a groupconsisting of Ag, Ag/Pd, Cu, Ni, Pt, Au, Pd or other such metals.

[0015] In some exemplary embodiments, a least one blank ceramic layer islocated in the stack such that the device will be provided withpredetermined resistance and capacitance values. Often, the terminationsmay comprise an inner layer having a metal oxide material and an outerlayer of solderable metal. In some exemplary embodiments, two of thesecond electrode plates may occupy respective topmost and bottommostpositions in the stack to enhance electrical shielding of an interiorthereof.

[0016] Other objects of the invention are achieved by an array devicehaving a predetermined number of RC circuits in a singular package. Thedevice comprises a device body defined by a plurality of first ceramiclayers and a plurality of second ceramic layers arranged to form astack. Each of the first ceramic layers has a plurality of side-by-sidefirst electrode plates thereon, the first electrode plates being atleast partially formed of a cofirable resistor material. Each of thesecond ceramic layers has a second electrode plate extending in adirection transverse to the first electrode plates. A predeterminednumber of the first ceramic layers are respectively adjacent to acorresponding one of the second ceramic layers such that the firstelectrode plates will oppose the second electrode plate to form twoplates of a capacitor of a respective RC circuit.

[0017] The device body is also configured having a plurality ofterminations on side surfaces thereof. Respective first electrode platescorresponding to one of the RC circuits are electrically connected to atleast one of the terminations. Furthermore, the second electrode platesare electrically connected to at least another of the terminations.

[0018] In some exemplary embodiments, a plurality of third ceramiclayers are arranged in the stack with the first ceramic layers andsecond ceramic layers. The third ceramic layers have thereon a pluralityof side-by-side third electrode plates at least partially formed of acofirable resistor material. A predetermined number of the third ceramiclayers are respectively adjacent to a corresponding one of the secondceramic layers such that the third electrode plates will oppose thesecond electrode plates to form two plates of a capacitor of arespective RC circuit. Respective third electrode plates correspondingto one of the RC circuits are connected to a corresponding one of theterminations.

[0019] In such embodiments, the first ceramic layers may be alternatelystacked with the second ceramic layers in a top portion of the devicebody. The third ceramic layers may then be alternated with the secondceramic layers in a bottom portion of the device body.

[0020] Other objects of the present invention are achieved by aminiature surface mount device comprising a device body having a unitarystructure characteristic of a plurality of stacked, pressed and sinteredceramic-electrode layers. The device body includes at least twoelectrical terminations located on side surfaces thereof. Each of theterminations comprises an inner termination layer having a metal oxidematerial and an outer termination layer of solderable metal.

[0021] In some exemplary embodiments, the inner termination layercomprises a metal oxide-glass frit layer substantially similar to amaterial used to form resistive electrodes in the device. Often, it willbe desirable to provide an intermediate termination layer of aconductive metal-glass frit between the inner termination layer and theouter termination layer. For example, the intermediate termination layermay comprise a silver-glass frit layer. In other embodiments, the outertermination layer is directly juxtaposed to the inner termination layer.Often, at least some ceramic-electrode layers of the miniature surfacemount device will comprise a metal oxide electrode material, such asruthenium oxide, mixed with a glass frit binder.

[0022] Still further objects of the invention are achieved by a methodof fabricating a composite RC device. According to the method, aplurality of first ceramic layers are provided having a predetermineddielectric constant. A first selected electrode pattern is entirelyformed on the first ceramic layers of a substantially nonresistiveconductive material. In addition, a plurality of second ceramic layersare provided having the predetermined dielectric constant. A secondselected electrode pattern is entirely formed on the second ceramiclayers of a cofirable resistive material. The second electrode patternis further configured so as to yield a desired resistance value.Furthermore, the first selected electrode pattern and the secondselected electrode pattern are configured to provide a particularelectrode overlap to yield a desired capacitance value.

[0023] Additional objects of the invention are achieved by a compositeRC device comprising a device body having a unitary structurecharacteristic of a plurality of stacked, pressed and sinteredceramic-electrode layers. The device body includes at least twoelectrical terminations located on side surfaces thereof. Theceramic-electrode layers include a plurality of first ceramic layershaving thereon a pair of first electrode plates extending to arespective termination. The ceramic-electrode layers further include aplurality of second ceramic layers having thereon a second electrodeplate formed of a resistive material. The second ceramic layers areinterleaved with the first ceramic layers to produce overlaps betweeneach of the second electrode plates and a respective pair of the firstelectrode plates in an adjacent ceramic-electrode layer.

[0024] Other objects, features and aspects of the present invention areprovided by various combinations and subcombinations of the disclosedelements, which are discussed in greater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] A full and enabling disclosure of the present invention,including the best mode thereof, to one of ordinary skill in the art, isset forth more particularly in the remainder of the specification,including reference to the accompanying drawings, in which:

[0026]FIG. 1 is a perspective view of a surface mount RC filter arrayconstructed in accordance with the present invention in position on acircuit board;

[0027]FIG. 2 is an enlarged perspective view of the filter array of FIG.1;

[0028]FIG. 3 is a cross sectional view as taken along line 3-3 of FIG.1;

[0029]FIGS. 4A and 4B are plan views of a first layer and a second layeras may be alternated and stacked to form the filter array of FIG. 1;

[0030]FIG. 5 is an electrical schematic showing an equivalent circuitrealized by the filter array of FIG. 1;

[0031]FIGS. 6A and 6B are cross-sectional views similar to FIG. 3illustrating the manner in which device capacitance can be adjustedindependently of device resistance in the array device of FIG. 1;

[0032]FIG. 7 is a perspective view of a discrete RC filter deviceconstructed in accordance with the present invention;

[0033]FIGS. 8A and 8B are plan views of a first layer and a second layeras may be alternated and stacked to form the filter device of FIG. 7;

[0034]FIG. 9 is a perspective view of an alternative RC filter arrayconstructed in accordance with the present invention;

[0035]FIGS. 10A, 10B and 10C are plan views of a first layer, a secondlayer and a third layer as may be alternated and stacked to form the RCfilter array of FIG. 9;

[0036]FIG. 11 is a cross-sectional view as taken along line 11-11 ofFIG. 9;

[0037] FIGS. 12A-B through 16A-B diagrammatically illustrate the mannerin which teachings of the present invention may be utilized to achieve avariety of configurations without altering exterior dimensions of thedevice;

[0038]FIG. 17 is a fragmentary view of a multilayer ceramic devicehaving a novel termination structure in accordance with the presentinvention;

[0039]FIG. 18 is an enlarged view of the area so indicated in FIG. 17;

[0040]FIG. 19 is a view similar to FIG. 18 illustrating an alternativetermination structure; and

[0041]FIG. 20 is a cross-sectional view showing the interiorconstruction of a still further alternative device constructed inaccordance with the present invention.

[0042] Repeat use of reference characters in the present specificationand drawings is intended to represent same or analogous features orelements of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0043] It is to be understood by one skilled in the art that the presentdiscussion is a description of exemplary embodiments only, and is notintended as limiting the broader aspects of the present invention, whichbroader aspects are embodied in the exemplary constructions.

[0044] The present invention discloses various improvements in surfacemount RC devices made according to multilayer ceramic techniques.Surface mount RC devices having internal resistor structures are shownin commonly-assigned U.S. Pat. No. 5,889,445, incorporated herein byreference. Generally, these devices are constructed having a unitarybody characteristic of a plurality of stacked, pressed and sinteredceramic-electrode layers. Terminations are applied to the surfaces ofthe body for electrical connection to external circuitry. According toindustry practice, the size of such devices may be expressed as a number“XXYY,” with XX and YY being the length and width in hundredths of aninch. Some typical sizes for devices of the present invention asexpressed under this practice are 0603, 0805, 1206, 1210 and 1812.

[0045]FIG. 1 illustrates a surface mount RC array 10 of the presentinvention mounted to a circuit board 12. As can also be seen in FIG. 2,array 10 includes a main body 14 of relatively small size. A pluralityof terminations 16 a-d and 18 a-d are located on respective sides ofmain body 14, with terminations 20 and 22 being similarly located atrespective ends thereof. While terminations 20 and 22 are here shownonly partially covering the end of main body 14, it is contemplated thatthese terminations may cover the entire end surface in some embodiments.

[0046] As shown in FIG. 1, the various terminations of the body 14 alignwith respective conductive paths, such as traces 24 and 26, defined onthe surface of circuit board 12. Electrical connection between eachtermination and its associated conductive path may be effected bysoldering. Typically, circuit board 12 may be made from alow-temperature organic material, with the solder being a lowtemperature eutectic solder applied by wave or reflow solderingtechniques.

[0047] Referring now to FIG. 3, the internal construction of main body14 will be explained. As can be seen, main body 14 includes a pluralityof first electrode plates (such as plates 28 d) situated in opposed andspaced apart relation with a plurality of second electrode plates 30.The electrode plates are separated by layers of ceramic material toprovide a predetermined dielectric constant. Capacitor body 14 istypically made by stacking ceramic-electrode layers formed usingconventional dicing techniques, which are then pressed and sintered in akiln. Generally, main body 14 will comprise approximately 5-50ceramic-electrode layers stacked in this manner.

[0048] As shown in FIG. 4A, each of the first electrode plates maycomprise a plurality of side-by-side electrode plates (designated 28a-d) formed on the surface of a first ceramic layer 31. In this case,each of the first electrode plates is configured to have a main plateportion (such as main plate portion 32) between a pair of tab portions(such as tab portions 34). The tab portions extend to, and areelectrically connected with, respective pairs of side terminations.

[0049] Referring now to FIG. 4B, each of the second electrode plates 30may be formed as a single electrode plate on the surface of a secondceramic layer 38. As shown, electrode plate 30, which has a main plateportion 40 between a pair of tab portions 42, preferably extends in adirection transverse to the direction of first electrode plates 28 a-d.Tab portions 42 are electrically connected with respective endterminations 20 and 22.

[0050] Preferably, electrode plates 28 a-d are at least partially formedof a cofirable resistor material, such as a combination including asuitable metal oxide and glass frit. For example, some presentlypreferred embodiments employ ruthenium oxide as the metal oxidematerial. As a result, the electrode pattern not only serves as oneplate of a capacitor, but also serves as a resistor. The use of acofirable material permits single fire processing, which simplifiesprocessing in relation to many prior art arrangements.

[0051] In the illustrated embodiment, electrode plates 28 a-d areentirely formed from the resistor material. The opposed capacitor plates30 are preferably formed of a conductive material from the family ofnoble and base metals that are traditionally used in cofired electroniccomponents and packages. For example, capacitor plates 30 may be formedfrom Ag, Ag/Pd, Cu, Ni, Pt, Au, Pd or the like. In some embodiments,however, it may be desirable to also form electrode plates 28 a-d of thecofirable resistor material.

[0052] As will be appreciated, the illustrated embodiment provides atotal of four RC devices in a single package. Often, each pair of sideterminations will serve as the respective input and output terminals ofone RC device. One or both of the end terminals 20 and 22 may begrounded to provide a three-terminal feedthrough arrangement, asschematically illustrated in FIG. 5.

[0053] In the illustrated embodiment, the R and C values of therespective RC devices can be adjusted by varying the overall number ofceramic layers. Due to the parallel arrangement of the resistors, moreplates 28 will yield a lower R value. Because parallel capacitors areadditive, fewer plates 30 will yield a lower C value. The values of Rand C can be adjusted independently by selectively applying the“capacitor” or “resistor” layers.

[0054] This can be explained most easily with reference to FIGS. 6A and6B. In FIG. 6A, array 10 is constructed so that every potential positionfor an electrode plate is populated. The resistance between terminal 16d and 18 d is determined by the single layer resistance of each plate 28d, and the number of layers in parallel. Capacitance is determined bythe number of combinations of plates 28 d and plates 30. Thus, devicecapacitance can be adjusted independently of device resistance byaltering the structure within the cofired body. Specifically, it ispossible to vary the values of resistance and/or capacitance byinterrupting the usual sequence of the plates.

[0055] In this regard, FIG. 6B illustrates a device 10′ wherein twoplate positions that could be occupied by a plate 30 are shown to bevacant. As a result, device 10′, otherwise identical to device 10, willexhibit a lower capacitance. Because the number of plates 28 d remainsthe same, however, the resistance between terminations 16 d and 18 dremains unchanged.

[0056]FIG. 7 illustrates a discrete RC device 50 constructed inaccordance with the present invention. Like array 10, device 50 includesa device body 52 manufactured from a plurality of ceramic electrodelayers arranged to form a stack. A pair of terminations 54 and 56 arelocated on respective sides of device body 52, as shown. Terminations 58and 60 are located at the respective ends of device body 52.

[0057]FIGS. 8A and 8B illustrate the ceramic layers that can bealternated in the fabrication of device body 52. As shown in FIG. 8A,the first ceramic layer 62 has a first electrode plate 64 locatedthereon. The plates 64 are configured to extend between terminations 58and 60. Plate 64 may be formed entirely of a cofireable resistormaterial as described above.

[0058] As shown in FIG. 8B, each of the second ceramic layers 66includes a second ceramic plate 68, which serve as counterelectrodes inthe eventual capacitor. In this case, second electrode plates 68 areconfigured to have a main plate portion 70 and a pair of tab portions72. The tab portions 72 extend to respective terminations 54 and 56located on the lateral sides of device body 52. Depending on therequirements of a particular application, electrode plates 68 may beformed of a substantially nonresistive material, or may be formed of acofireable resistor material.

[0059]FIG. 9 illustrates an alternative embodiment which is similar inits external appearance to array 10. Specifically, FIG. 9 illustrates anarray 80 having a device body 82 formed of a plurality ofceramic-electrode layers arranged in a stack. The lateral sides of body82 carry a plurality of opposite terminations 84 a-d and 86 a-d.

[0060] In this case, array 80 is configured to yield a total of eightdifferent RC circuits in a single package. Instead of three-terminalfeedthrough arrangements as described above, the RC circuits of array 80are configured as two terminal series circuits.

[0061] FIGS. 10A-10C illustrate the three different ceramic layers thatcan be stacked in the manufacture of device body 82. As shown in FIG.10A, first ceramic layer 92 includes a total of four electrode plates 94a-d. As shown, plates 94 a-d are arranged side by side, with the tabportion of every other plate extending to opposite sides of the device.Thus, electrode plates 94 a and 94 c will be electrically connected toterminations 84 a and 84 c, with electrode plates 94 b and 94 d beingconnected to terminations 86 b and 86 d, respectively.

[0062] Referring to FIG. 10B, the second ceramic layers 96 each includean elongate electrode plate 98 extending to opposite ends of device body82. As such, electrode plates 98, which will serve as counter electrodesin the multilayer capacitor structure, will be electrically connected toterminations 88 and 90.

[0063] Referring now to FIG. 10C, third ceramic layer 100 includes aplurality of third electrode plates 102 a-d. Like electrode plates 94a-d, electrode plates 102 a-d are arranged such that the tab portion ofevery other plate extends to opposite sides of device body 82. Thus,electrode plates 102 a and 102 c will be electrically connected toterminations 86 a and 86 c, respectively. Similarly, electrode plates102 b and 102 d will be electrically connected to terminations 84 b and84 d.

[0064] Preferably, electrode plates 94 a-d and 102 a-d are formed of acofireable resistor material as described above. In such embodiments,electrode plates 98 will often be formed of a substantially nonresistivematerial. In this manner, each of the RC circuits may have substantiallyequivalent values of both resistance and capacitance.

[0065] Embodiments are also contemplated, however, in which onlyelectrode plates 98, or all of the electrode plates in the device, areformed of the resistive material. Such a construction may beadvantageous to provide different values of resistance among the variousRC circuits in the array. For example, the interior circuits may have ahigher resistance value if electrode plates 98 are made of a resistivematerial, since there will be a longer resistive path from thecounterelectrode of the capacitor to the end termination for thesecircuits.

[0066]FIG. 11 illustrates one stacking arrangement which may be utilizedto produce array 80. In this case, the first ceramic layers arealternated with the second ceramic layers in the top portion of thestack. In the bottom portion of the stack, the second ceramic layers arealternated with the third ceramic layers. According to one preferredarrangement, second electrodes 98 will occupy both the topmost andbottommost positions in the stack. This is advantageous to provide adegree of electrical shielding to the interior of the device.

[0067] As noted above, the present invention provides a high degree offlexibility in the manufacturing process. Depending on the desiredvalues of resistance and capacitance, ceramic layers may be left blank,or the physical dimensions of the layers may be changed. A wide varietyof different circuits can be easily created within a single componentsize. A series of examples will now be described to demonstrate thisflexibility.

[0068]FIGS. 12A and 12B are side and transverse sectional views,respectively, diagrammatically illustrating the construction of atypical multilayer ceramic capacitor 108. As can be seen, a plurality offirst polarity plates 110 are interleaved with a plurality of secondpolarity plates 112, which extend to opposite ends of body 114. In thisprior art arrangement, the capacitor plates are formed of a conductivematerial, such as Ag/Pd.

[0069]FIGS. 13A and 13B illustrate an RC device wherein the oppositepolarity plates are made from a cofireable resistive material, such asruthenium oxide and glass frit. Device 208 will exhibit a capacitancesubstantially identical to that of device 108 but will have a muchhigher series resistance value.

[0070]FIGS. 14A and 14B illustrate a further alternative 308 whereinfirst polarity plates 310 are formed from the resistive material. Secondpolarity plates 312, on the other hand, are formed in this case from theconductive material. Device 308 will exhibit a capacitance substantiallyidentical to that of devices 108 and 208, but will exhibit a greatlyreduced value of resistance.

[0071]FIGS. 15A and 15B illustrate an RC device 408 having firstpolarity terminals 410 made from the resistive material. Electrodeplates 412, on the other hand, are formed of the conductive material. Inthis case, electrode plates 412 are configured to provide a smalleroverlap area than in the embodiments discussed above. As a result,device 408 will exhibit a smaller capacitance. In addition, theresistance value will be lower than that of devices 208 and 308 due tothe shorter length of resistive material.

[0072]FIGS. 16A and 16B illustrate a still further alternative device508, in which the first polarity electrode plates 510 are made from theresistive material. Electrode plates 512, on the other hand, are formedfrom the conductive material. It can be seen that plates 510 areconfigured to have a length and area approximately equivalent to plates310 of device 308. Plates 512, however, are configured to have arelatively narrow width. Thus, in comparison to device 308, device 508will exhibit a lower capacitance value. The resistance value, however,will not be substantially changed.

[0073] The following table represents theoretical capacitance andresistance values that may be achieved in one family of examples asdescribed above, assuming use of ruthenium oxide as the resistivematerial and Ag/Pd as the conductive material: DEVICE RESISTANCECAPACITANCE 108 0.006 Ohms  39.6 pF 208 80.1 Ohms 39.6 pF 308 43.0 Ohms39.6 pF 408 26.3 Ohms 19.9 pF 508 35.3 Ohms 21.8 pF

[0074] Thus, within a single component size, the present inventionallows a wide variety of different RC circuits to be manufactured tomeet the needs of a particular application.

[0075] The above examples demonstrate that variations in plate geometrycan yield different resistance and capacitance values. Furthervariations can be achieved, however, by altering the materials fromwhich the electrode plates are made. For example, a conductive metal,such as silver, may be selectively added to the metal oxide/glass fritmaterial to lower the resistance of the material.

[0076] The present invention also provides an improved terminationstructure for use with a multilayer ceramic device. Referring now toFIG. 17, a termination 120 of the present invention is shown covering anend surface of a device body 122. As can be seen in FIG. 18, termination120 includes an inner termination layer 124 and an outer terminationlayer 126.

[0077] Where the device includes internal electrodes formed of a ceramicmaterial, such as the metal oxide and glass frit material describedabove, inner layer 124 is preferably formed from a chemically similarmaterial. For example, in one preferred implementation, the terminationmaterial may be made from about equal parts of RuO₂ and glass frit,which is fired onto the body 122 when it is sintered. Although layer 124is made from a resistive material in this example, it will not addappreciable resistance to the overall device. This is due to therelatively small thickness of the resistive layer.

[0078] Termination layer 126, on the other hand, is typically formed ofSnPb, Ni or other solderable metal. Preferably, layer 126 is applied tothe device body after sintering as has been done in the past.

[0079] When the improved termination of the present invention is usedwith an RC device having resistive electrodes, inner termination layer124 may be formed from an identical material. Because the two materialsare the same, the termination will readily bond with the internalelectrodes during the firing process. This is in contrast with fired-ontermination materials of the prior art, such as a silver-glass fritmaterial, which may not readily adhere to a metal oxide electrode.

[0080]FIG. 19 illustrates an alternative termination structure 120′constructed in accordance with the present invention. Terminationstructure 120′ includes an inner termination layer 124′ and an outertermination layer 126′ similar to layers 124 and 126, respectively. Inthis case, an intermediate termination layer 128 is provided betweentermination layers 124′ and 126′. Termination layer 128 is formed of aprior art fired-on termination material of conductive metal and glassfrit. For example, a silver/glass frit material of the type typicallyused in component terminations of the prior art may be used for thispurpose. Structure 120 may be advantageous to provide a good bond toresistive internal electrodes, while at the same time otherwiseappearing as a termination structure of the prior art.

[0081] An improved termination structure made in accordance with thepresent invention has been found to offer a number of benefits incertain applications. For example, where an internal electrode ofresistive material is used, the like material of the terminationstructure provides excellent electrical contact. In addition, thetermination structure will provide excellent electrical contact toconductive internal electrodes such as Ag/Pd electrodes and the like.The termination structure will also achieve excellent mechanical bond tothe ceramic chip itself for a strong, well-adhered termination.Moreover, the metal oxide termination offers very well-matched thermalexpansion properties between the chip and termination to reducethermal-cycle induced failures.

[0082] In the above embodiments, resistive electrodes have been shownabove as forming the entire electrode pattern. Embodiments arecontemplated, however, wherein part of the electrode is formed fromresistive material and part is formed from a traditional conductivematerial. In this regard, a conductive tab may be provided between thetermination and an electrode plate formed of resistive material. Thismay be particularly advantageous where it is desired to utilize atraditional conductive metal/glass frit termination material as theinner layer of the termination structure. Alternatively, the electrodeplate may be formed of a conductive material, with the resistivematerial forming a series resistor between it and the termination.

[0083]FIG. 20 illustrates a still further embodiment constructed inaccordance with the present invention. In this case, a device 130 isdepicted having terminations 132 and 134 located at respective ends of asintered body 136. Each of the first ceramic layers defines a pair ofconductive capacitor plates 138 a-b extending to a respectivetermination. The second ceramic layers each define a resistive plate 140which is not directly connected to either of the terminations. Instead,resistive plates 140 are configured to overlap a portion of plates 138a-b to yield a predetermined capacitance. Electrically, the resultingstructure will be equivalent to a series capacitor-resistor-capacitor,wherein the resistance and capacitance values can be adjusted asdescribed above.

[0084] It can thus be seen that the present invention provides improvedRC devices that accomplish the various objectives set forth above. Whilepreferred embodiments of the invention have been shown and described,modifications and variations may be made thereto by those of ordinaryskill in the art without departing from the spirit and scope of theinvention. It should also be understood that aspects of the variousembodiments may be interchanged both in whole or in part. Furthermore,those of ordinary skill in the art will appreciate that the foregoingdescription is by way of example only, and is not intended to belimitative of the invention so further described in the appended claims.

What is claimed is:
 1. An array device having a predetermined number ofRC circuits in a singular package, said device comprising: a device bodydefined by a plurality of first ceramic layers and a plurality of secondceramic layers arranged to form a stack; each of said first ceramiclayers having thereon a plurality of side-by-side first electrodeplates, said first electrode plates being at least partially formed of acofirable resistor material; each of said second ceramic layers having asecond electrode plate extending in a direction transverse to said firstelectrode plates, a predetermined number of said first ceramic layersbeing respectively adjacent to a corresponding said second ceramic layersuch that said first electrode plates will oppose said second electrodeplate to form two plates of a capacitor of a respective RC circuit; andsaid device body having a plurality of terminations on side surfacesthereof, respective of said first electrode plates corresponding to oneof said RC circuits being electrically connected to at least one of saidterminations and said second electrode plates being electricallyconnected to at least another of said terminations.
 2. An array deviceas set forth in claim 1, further comprising: a plurality of thirdceramic layers arranged in said stack with said first ceramic layers andsaid second ceramic layers, said third ceramic layers having thereon aplurality of side-by-side third electrode plates at least partiallyformed of a cofirable resistor material; a predetermined number of saidthird ceramic layers being respectively adjacent to a corresponding oneof said second ceramic layers such that said third electrode plates willoppose said second electrode plates to form two plates of a capacitor ofa respective RC circuit; and respective of said third electrode platescorresponding to one of said RC circuits being connected to acorresponding one of said terminations.
 3. An array device as set forthin claim 2, wherein said first ceramic layers are alternately stackedwith said second ceramic layers in a top portion of said device body andsaid third ceramic layers are alternated with said second ceramic layersin a bottom portion of said device body.
 4. An array device as set forthin claim 3, wherein each of said first electrode plates is electricallyconnected only to a respective one of said terminations.
 5. An arraydevice as set forth in claim 4, comprising a total of four of saidside-by-side first electrode plates on each of said first ceramic layersand a total of four of said side-by-side third electrode plates on eachof said third ceramic layers.
 6. An array device as set forth in claim4, wherein said cofirable resistor material comprises ruthenium oxide.7. An array device as set forth in claim 2, wherein each of said firstelectrode plates is electrically connected between first and secondterminations, said first and second terminations being located onopposite sides of said device body.
 8. An array device as set forth inclaim 2, wherein each of said second electrode plates extend betweenthird and fourth terminations located at respective opposite ends ofsaid device body.
 9. An array device as set forth in claim 2, whereinsaid second electrode plates are formed of a substantially nonresistiveconductive material.
 10. An array device as set forth in claim 9,wherein said substantially nonresistive conductive material is selectedfrom a group consisting of Ag, Ag/Pd, Cu, Ni, Pt, Au and Pd.
 11. Anarray device as set forth in claim 2, wherein said cofirable resistormaterial comprises ruthenium oxide.
 12. An array device as set forth inclaim 2, further comprising at least one blank ceramic layer located insaid stack such that said device will be provided with predeterminedresistance and capacitance values.
 13. An array device as set forth inclaim 2, wherein two of said second electrode plates occupy respectivetopmost and bottommost positions in said stack to enhance electricalshielding of an interior thereof.
 14. A composite RC device, said devicecomprising: a device body defined by a plurality of first ceramic layersand a plurality of second ceramic layers arranged to form a stack; eachof said first ceramic layers having thereon at least one first electrodeplate; each of said second ceramic layers having a second electrodeplate, a predetermined number of said first ceramic layers beingrespectively adjacent to a corresponding said second ceramic layer suchthat said first electrode plate will oppose said second electrode plateto form two plates of a capacitor; said first electrode plates or saidsecond electrode plates being at least partially formed of a cofirableresistor material; and said device body having a pair of terminationselectrically connected to said first electrode plate on each of saidfirst ceramic layers, and further having at least one terminationelectrically connected to said second electrode plate on each of saidsecond ceramic layers to provide a predetermined electrical function;wherein two of said second electrode plates occupy respective topmostand bottommost positions in said stack to enhance electrical shieldingof an interior thereof.